1. Technical Field
The present invention relates to a vehicle safety apparatus including an inflatable vehicle occupant protection device, such as an air bag. In particular, the present invention relates to a timing circuit for enabling operation of an air bag disable switch and an associated indicator when the vehicle ignition is off.
1. Description of the Prior Art
It is known to inflate an air bag to help protect a front seat passenger of a vehicle in the event of a vehicle collision. The air bag is stored in a deflated condition, together with an inflator, in the instrument panel of the vehicle. In the event of a vehicle collision, the inflator is actuated, and the air bag is inflated into a position between the front seat passenger and the instrument panel of the vehicle.
It is sometimes desirable that a passenger side air bag not be inflated in the event of a vehicle collision, for example, if a rearward facing child seat is disposed on the vehicle seat. It is known to provide a disable switch on the instrument panel of the vehicle, into which the vehicle ignition key can be inserted and turned in order to disable actuation of the inflator for the passenger side air bag. The disable switch is electrically connected with an indicator, such as a warning lamp, which indicates that the switch is in the "disabled" condition and that actuation of the inflator is not enabled.
If the indicator is connected at all times to the vehicle battery, then the indicator can alert a vehicle occupant, even when the vehicle ignition is off, that the switch is in the "disabled" condition. In this case, however, the indicator can, undesirably, drain the vehicle battery if the vehicle is not run for an extended period of time.
If the indicator is not connected at all times to the vehicle battery, then the indicator is not energized if the switch is in the "disabled" condition when the occupant enters the vehicle. In this case, the occupant does not know whether actuation of the air bag is enabled, until the vehicle ignition is turned on. Also, the indicator is not energized if the vehicle occupant moves the switch to the "disabled" condition upon entering the vehicle and prior to turning on the vehicle ignition. In either case, the vehicle ignition may have to be turned off and the ignition key removed in order to move the disable switch to the desired position.